Vapor phase corrosion inhibitor-desiccant material

ABSTRACT

A vapor phase corrosion inhibitor-desiccant composite comprising silica gel granules coated with a vapor phase corrosion inhibitor component. The corrosion inhibitor component is selected from a formulation comprising anhydrous molybdates such as ammonium dimolybdate, sodium molybdate and amine molybdates mixed with benzotriazole and sodium nitrate, or from a formulation comprising amine benzoates, amine nitrates and benzotriazole. The composites can be impregnated into foam, extruded with polyolefin films which can additionally be laminated with metallized second film, or encapsulated in an air-permeable container. The corrosion inhibitor formulations have vapor pressures which provide ongoing corrosion protection for susceptible articles situated favorably with respect to the composite.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of co-pending application Ser. No. 07/929,621,filed on Aug. 13, 1992, now pending, which is a continuation-in-part ofour co-pending application Ser. No. 905,953, filed Jun. 29, 1992 nowU.S. Pat. No. 5,209,869 which in turn was a continuation-in-part of ourco-pending application Ser. No. 07/594,357, filed Sep. 27, 1990, nowU.S. Pat. No. 5,139,700 allowed Apr. 3, 1992 and entitled "VAPOR PHASECORROSION INHIBITOR MATERIAL", which in turn, was a continuation-in-partof our co-pending application Ser. No. 07/417,238, filed Oct. 5, 1989,entitled "VAPOR PHASE CORROSION INHIBITOR MATERIAL", now abandoned,which in turn was a continuation-in-part of application Ser. No.07/235,120, filed Aug. 23, 1988, entitled "VAPOR PHASE CORROSIONINHIBITOR MATERIAL", now abandoned.

FIELD OF THE INVENTION

The present invention relates to a formulation which is particularlyadapted for use as a vapor phase corrosion inhibitor-desiccant, thematerial being useful for either inhibiting the corrosion of themetallic items and/or passivating the surfaces thereof, the formulationbeing particularly adapted for direct incorporation within foam byimpregnation therein or within synthetic resinous films throughextrusion or deposition into a film, such as into an olefinic film,polyethylene, or the like. Film products prepared in accordance with thepresent invention find particular application in the formation ofenclosures about metallic articles susceptible to corrosion, and providea relatively dry corrosion inhibiting atmosphere therewithin.Air-permeable capsules and impregnated foam products prepared inaccordance with the invention find application in their placement at thesite of the items to be protected.

Specifically, the compositions of the present invention comprise a vaporphase corrosion inhibitor-desiccant wherein the vapor phase corrosioninhibitor component is selected from the group consisting of anhydroussodium molybdate and mixtures of such molybdates with sodium nitrite andbenzotriazole, and mixtures of benzoates of amine salts withbenzotriazole and nitrates of amine salts. The desiccant component ofthe composition is a solid-phase granular particle consistingessentially of silica gel onto which the vapor phase corrosion inhibitorcomponent, in powdered form, has been deposited thereon. Thesecompositions provide a vapor phase corrosion inhibitor-desiccant whichmay be extruded along with a film material, with the film thereafterbeing utilized to form an enclosure housing the item or items beingprotected. Alternatively, the compositions may be placed withinenclosures or packages containing items which are to be protected fromcorrosion. One manner in which this approach is effective is to providean air-permeable capsule or other similar container containing thecompositions therein. Of course, the capsule or other container musthave sufficient permeability so that the components of the corrosioninhibitor-desiccant therein can enter the ambient environment of theitems to be protected. A second manner in which the corrosioninhibitor-desiccant compositions can be placed within enclosures orpackages containing items to be protected is to impregnate foam with thecompositions and then place the foam in proximity to the items.

For most purposes, anhydrous powdered or finely divided mixtures ofcertain molybdates including anhydrous sodium molybdate, ammoniumdimolybdate and amine molybdates along with mixtures of such molybdateswith sodium nitrite and benzotriazole and mixtures of amine benzoateswith amine nitrates and benzotriazole are preferred. These materials arethen deposited upon the larger silica gel granules, with such vaporphase corrosion inhibitor components being preferred for such depositionapplications. This composite mixture is preferably extruded intopolyethylene film at a concentration of from between about 2% and 3% byweight. It is preferably impregnated into foam at a concentration offrom between about 1% and 30% by weight. Preferably, the silica gelparticulate material has an average particle size ranging from betweenabout 2 μm and 8 μm, with the vapor phase corrosion inhibitor componentdeposited on the surface of the granules having a size ranging frombetween about 0.001 micron and 0.1 micron.

As an added feature of the invention, film materials extruded with theformulations of the present invention may, in turn, be laminated to asecond metallized film, such as, for example, metallized polyethyleneterephthalate. The combined laminate provides a means to reduce and/oreliminate static build-up in or along the film, and accordingly improvesthe properties of the film when employed as an enclosure.

BACKGROUND OF THE INVENTION

In commerce and industry today, the useful life of corrodible items maybe extended and/or preserved by providing corrosion inhibitors whichprotect the corrodible item from the adverse effects of its ambientenvironment. Corrosion inhibitors, particularly vapor phase corrosioninhibitors, have been found useful in protecting certain corrodibleitems against reaction with elements or compounds which may be foundwithin their environment, and thereby losing their effectiveness,reducing their useful life, or otherwise diminishing their value. Suchprotection is typically needed during times of packaging, handling,shipment, or during end use. Elements or compounds which are normally ofprimary concern are gases such as oxygen, water vapor, sulfides, carbondioxide, and the like. The vapor phase corrosion inhibitor-desiccantformulations of the present invention find particular application in thepreparation of packaging material and in the preparation offormulation-impregnated foam. Packaging material is produced throughin-situ extrusion of the material with films, with the films thereafterbeing utilized to form an envelope or other enclosure about the articlebeing protected. The films may also be employed as a member of amulti-layer laminate including a metallized film having good tearresistant properties such as stress-oriented polyethylene terephthalatecontaining a vapor deposited film or layer of metallic aluminum on asurface thereof. Such films are commercially available and are commonlydesignated as "aluminized" films. Foam impregnation is accomplished byliquid dispersion, as known in the art, of the formulations into thefoam, followed by controlled evaporation of the liquid carrier tothereby deposit the formulations in the cellular interstices of thefoam. The resultant product can be placed in proximity to items to beprotected, with such protection occurring as the corrosioninhibitor-desiccant is released from the foam.

Among the common indications of corrosion manifested in useful metallicarticles are oxidation, pitting, tarnishing, mottling, or discolorationof the surfaces of these items. These manifestations occur in thearticles, particularly when exposed to oxygen and in either gaseous orliquid phase. Additionally, sulfides may present corrosion or tarnishingproblems as well. Inasmuch as both oxygen and water, including watervapor, occur normally and are available in nature, it is normallynecessary to take precautions against corrosion when packaging metallicitems for shipment or storage, or when subjecting such items to normaluse. Metals which are frequently found to be susceptible to corrosionunder normal atmospheric and ambient conditions are iron, copper, brass,aluminum, silver, and alloys of these metals. The formulations of thepresent invention are particularly useful in providing protection toboth ferrous and non-ferrous metals, including such non-ferrous metalsas aluminum, copper and brass. Care must frequently be taken to protectarticles fabricated from such metals, even when their surfaces have beentreated so as to be provided with sacrificial or aesthetic coatings ofzinc or cadmium on their surfaces. Such sacrificial or aestheticcoatings are, of course, in wide use, but restrictions of use of thesematerials may appear from time to time due to their potentialcontribution to pollution or the like. Accordingly, means must beprovided to find alternate techniques for the protection and/orpreservation of metallic articles.

In the past, it has been known to provide a package or other enclosurewhich includes one or more inhibiting compounds along with thecorrodible item or items to be protected. Additionally, articles havebeen protected by means of utilization of protective coatings in theform of solids, liquids, greases, or pastes, however such coatings tendto be temporary in nature and further present certain disadvantages tonormal handling and packaging. Furthermore, removal of such protectivecoatings may present problems either due to incomplete removal, or thecosts of such removal. The composite vapor phase corrosioninhibitor-desiccant materials of the present invention find applicationas a solid phase composite which may be impregnated into foam or beco-extruded with film which is to form an enclosure about an articlebeing protected.

Solid phase and liquid phase compounds have been used in the past toprovide a source of vapor phase corrosion inhibitors. These materialstypically undergo either evaporation or sublimation so as to provide thesubstantially constant availability of the inhibitors. In other words,vapor phase corrosion inhibitors typically emit vapors which protectcorrodible surfaces through the deposition or condensation of aprotective film or coating upon the surface. In order to be assured thata constant supply of inhibitor be present, adequate quantities of thesolid phase or liquid phase corrosion inhibiting compounds must beprovided, with the corrosion inhibiting compounds being released at oradjacent the location where needed.

Granular silica gel is widely available for use as a desiccant.Frequently, granular silica gel is placed within a woven or knit pouchand placed within the confines of a package or enclosure for envelopinga corrosion-susceptible article. The granular material, when maintainedat a particle size of below about 8 μm may be utilized as a solid-phasesubstrate upon which powdered vapor phase corrosion inhibitor materialsmay be deposited.

When a laminate is formed in which one layer comprises a heat sealablefilm such as polyethylene with composite compositions of the presentinvention extruded in-situ, and with a second film layer being amaterial such as metallized stress-oriented polyethylene terephthalatefilms with desirable combinations of properties are achieved.Specifically, the polyethylene film layer retains its conventional heatsealing properties, while the stress-oriented polyethylene terephthalateprovides a tear-resistant property. The metallized layer is utilized toreduce and/or eliminate static build-up, thereby further enhancing theproperties and qualities of the laminate. Stress-oriented polyethyleneterephthalate is normally biaxially oriented, and is, of course,commercially available. The composite vapor phase corrosioninhibiting/desiccant materials of the present invention enhance theprotective qualities of films which incorporate or otherwise include thecomposite materials.

SUMMARY OF THE INVENTION

In accordance with the present invention, a solid phase material hasbeen found which provides a source of vapor phase corrosion inhibitingmaterial along with a substrate of granular silica gel. The vaporpressure of the composite material is balanced with the quantitiesnormally required to be emitted for effective and long term protectionof the metallic surfaces being exposed for treatment. The formulationsof the present invention provide for emission of vapors in aconcentration which is appropriate for strong protection of the metallicsurfaces, and yet at a rate sufficiently low so as to provide forrelatively long-lasting and long-term effective economic treatment. Thepresence of granular silica gel as a substrate for the vapor phasecorrosion inhibiting component has been found to enhance the protectivequalities of the product. The formulations of the present invention arecompatible with and may be impregnated into foam such as anisocyanate-derived polymer foam, or extruded or otherwise deposited withsynthetic resinous films, such as aliphatic hydrocarbon or olefinicfilms such as polyethylene and polypropylene. Such films may beincorporated with other films in a laminate, and in particular may becombined with a metallized film so as to enhance the static eliminationand mechanical properties of the composite.

Additionally, the vapor phase corrosion inhibitor-desiccant compositesof the present invention have been found to produce little, if any,visible residue. The lack of residue enhances the utility of thematerials, inasmuch as little, if any, mechanical or electrical problemsresult from the continuous use of these materials. Additionally, whengranular silica gel component is used as a substrate for the corrosioninhibitor component, smoke and fume evolution of the corrosion inhibitorcomponent is greatly reduced.

Typical corrosion inhibiting articles and materials used in the past aredisclosed in Miksic et al U.S. Pat. Nos. 4,051,066 and 4,275,835.

The composite formulations of the present invention have been found tobe particularly well adapted to be housed in an air-permeable capsulefor placement with an item to be protected, to be impregnated into foam,or to be combined as an extrudate with films fabricated from aliphatichydrocarbon such as polyethylene and polypropylene. For facilitatingimpregnation or extrusion operations, composites consisting of powderedanhydrous molybdates such as ammonium dimolybdate, sodium molybdate andamine molybdates mixed with benzotriazole and sodium nitrate or aminebenzoates mixed with amine nitrates and benzotriazole are deposited upongranular silica gel particles. These composites are, in turn,impregnated into the foam or co-extruded with appropriate film-formingmaterials. Generally speaking, the formulations of the present inventionare utilized for retention and/or packaging within modestly porousenvelopes or other enclosures formed of plastic film or plastic foam.Typically, those certain enclosures disclosed and claimed in the Miksicet al U.S. Pat. Nos. 4,051,066 and 4,275,835, as identified hereinabove,are well adapted for use with the formulations or compounds of thepresent invention. Also, when extruded with a heat sealable film such aspolyethylene, a metallized (aluminized) layer such as biaxiallystress-oriented polyethylene terephthalate may be employed to enhancethe mechanical properties of the overall film arrangement. Techniquesfor laminating these films together are, of course, well known in theart.

In accordance with the present invention, the vapor phase corrosioninhibitor components comprising molybdates which have been foundparticularly desirable for use in combination with metallic surfacessusceptible to corrosion comprise anhydrous sodium molybdate [Na₂ Mo O₄], anhydrous ammonium dimolybdate [(NH₄)₂ Mo O₄ ], or an anhydrousamine-molybdate having the general structural formula: ##STR1## whereinR₁ is an aliphatic hydrocarbon having up to 7 carbon atoms, and whereinR₂ is either hydrogen or an aliphatic hydrocarbon having up to 7 carbonatoms. The preferred amine molybdates of this component of thecomposites of the present invention are amine-molybdates derived fromthe group consisting of dicyclohexylamine, 2-ethylhexylamine, andcyclohexylamine. Such molybdates are readily synthesized and can beprepared in anhydrous form without requiring unusual processing orhandling problems. As indicated above, these molybdates are utilized inanhydrous form when provided in a permeable capsule, impregnated into afoam, or extruded with a film, and are employed in a mixture incombination with sodium nitrite and benzotriazole. Alternatively,anhydrous sodium molybdate and ammonium dimolybdate may be utilized incombination with sodium nitrite and benzotriazole. A second group ofcomponents also having particularly desirable utility as vapor phasecorrosion inhibitor components is a mixture comprising amine benzoates,amine nitrates and benzotriazole. A preferred composition comprisescyclohexylamine benzoate, ethylamine benzoate, dicyclohexylamine nitrateand benzotriazole. In use, these materials provide a highly desirablebalance between continuous emission from the solid phase, with thisemission being at a rate sufficiently low so as to provide forrelatively effective long-term and economic protection and treatment.

The granular silica gel component of the present invention preferablyhas a particle size range of less than about 8 μm. Such granular silicagel is, of course, widely commercially available and as indicated above,provides a solid phase substrate for the vapor phase corrosion inhibitorcomponent.

It is therefore a primary object of the present invention to provide animproved vapor phase corrosion inhibitor-desiccant which is particularlyadapted for use in the protection of metallic surfaces exposed toenvironments which are corrosive to the exposed surfaces.

It is a further object of the present invention to provide an improvedvapor phase corrosion inhibitor-desiccant which is formulated so as topossess a vapor pressure or other property which allows transport of theinhibitor to the metal surface appropriate for transport of appropriatequantities of the inhibitor from solid phase in the film to the metalsurface, with the balance of the inhibitor being retained in the film,to provide a continuous supply of emitted corrosion inhibiting material.

It is yet a further object of the present invention to provide animproved vapor phase corrosion inhibitor-desiccant composite which isformulated so as to be capable of impregnation into a foam or extrusionwith conventional aliphatic hydrocarbon resinous films such aspolyethylene, polypropylene, and the like.

It is still a further object of the present invention to provide animproved vapor phase corrosion inhibitor-desiccant composite which isformulated so as to be capable of extrusion with conventional heatsealable films such as polyethylene, with such polyethylene films being,in turn, laminated to a metallized second film so as to enhancemechanical properties as well as static elimination properties of thecomposite laminate.

Another object of the present invention is to provide a foam productimpregnated with the vapor phase corrosion inhibitor-desiccant materialhere described.

Yet another object of the present invention is to provide anair-permeable capsule containing the vapor phase corrosioninhibitor-desiccant material of the present invention for placement inthe proximity of an item to be protected.

Other and further objects of the present invention will become apparentto those skilled in the art upon a study of the following specification,appended claims, and accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a typical laminate prepared inaccordance with the present invention, with the center or metallizedlayer being shown in somewhat exaggerated form due to limitations ofdraftsmanship;

FIG. 2 is an enlarged cross-section of an open cell foam within which acorrosion inhibitor-desiccant formulation is impregnated;

FIG. 3 is a roll or coil of the foam of FIG. 2; and

FIG. 4 is an air-permeable capsule in which a corrosioninhibitor-desiccant formulation is housed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with the preferred embodiment of the present invention, aparticularly useful vapor phase corrosion inhibitor component for thecomposite material to be supplied in an air-permeable capsule,incorporated with foam, or extruded polyethylene film includes a mixtureof either anhydrous sodium molybdate, anhydrous ammonium dimolybdate, oramine molybdates, together with sodium nitrite and benzotriazole.Specifically, in a particularly preferred embodiment, a mixture isprovided in the following formulation:

    ______________________________________                                        Component          Percent by Weight                                          ______________________________________                                        Anhydrous sodium molybdate                                                                       about 70%                                                  Sodium nitrite     about 25%                                                  Benzotriazole      about  5%                                                  ______________________________________                                    

This mixture is particularly effective when prepared in powdered formhaving a particle size below about 1 micron, and deposited upon granularsilica gel. The relative weight ratios are preferably from between about45% vapor phase corrosion inhibitor component, balance silica gel,although ratios of from between about 30% and 50% vapor phase corrosioninhibitor component, balance silica gel may be employed. The compositematerial is impregnated into foam at a concentration of from about 1% toabout 30% by weight. It is extruded into polyethylene film at aconcentration of from about 2% to about 3% by weight.

In the formulation provided above, the useful range of the componentspresent in the vapor phase corrosion inhibiting constituent may be setforth as follows:

    ______________________________________                                        Component          Percent by Weight                                          ______________________________________                                        Anhydrous sodium molybdate                                                                       about 65%-about 75%                                        Sodium nitrite     about 22%-about 28%                                        Benzotriazole      about  4%-about  6%                                        ______________________________________                                    

These ranges may be found useful for certain applications.

A second particularity useful vapor phase corrosion inhibitor componentfor the composite material comprises a mixture of amine benzoates, aminenitrates and benzotriazole. Specifically, the following formulationprovides a particularly preferred embodiment:

    ______________________________________                                        Component         Percent by Weight                                           ______________________________________                                        Cyclohexylamine benzoate                                                                        about 68%                                                   Ethylamine benzoate                                                                             about 10%                                                   Dicyclohexylamine nitrate                                                                       about 20%                                                   Benzotriazole     about  2%                                                   ______________________________________                                    

This mixture, also in powdered form and having a particle size belowabout 1 micron, is deposited upon granular silica gel, with relativeweight ratios the same as recited above for the formulations containingmolybdates. Likewise, its impregnation into foam or extrusion into filmis at the same concentration as stated for the molybdate formulations.The useful range of the preferred formulation shown above is as follows:

    ______________________________________                                        Component        Percent by Weight                                            ______________________________________                                        Cyclohexylamine benzoate                                                                       about 50%-about 97%                                          Ethylamine benzoate                                                                            about  1%-about 20%                                          Dicyclohexylamine nitrate                                                                      about  1%-about 20%                                          Benzotriazole    about  1%-about 10%                                          ______________________________________                                    

Preparation of compositions containing these components are prepared bysimply blending the individual powdered components together.

While there are various techniques that may be employed for providing anappropriate extrudate including, for example, polyethylene and a vaporphase corrosion inhibitor-desiccant of the type described herein, oneparticular technique has been found to be particularly useful.Specifically, the composite formulation is formed and rendered asuniform in particle size and configuration as possible. This compositeis then combined with a relatively limited quantity of polyethylene withthe mixture then being passed through the barrel of a conventionalextruder to form a master batch. The resultant master batch is thenchopped and rendered into pellet form. These pellets are, in turn,combined with additional polyethylene and then extruded as the filmcontaining a vapor phase corrosion inhibitor-desiccant of the typedescribed.

Preparation of a foam-impregnated product is accomplished by dispensinga corrosion inhibitor-desiccant formulation of the present invention ina liquid carrier in which the foam is then immersed. The formulationbecomes dispensed throughout the foam structure during immersion, and isthere retained upon removal of the foam from the liquid carrier.Subsequent evaporation of the carrier is effectuated to thereby yieldthe impregnated foam product. An adhesive backing can be applied to thefoam product to permit convenient placement and retention of the productat the site of needed protection.

A preferred air-permeable capsule product is constructed of a plasticvessel containing a corrosion inhibitor-desiccant formulation of thepresent invention and having an opening which is covered by anair-permeable Tyvek membrane (manufactured by Du Pont Co., Wilmington,Del.) through which emission of the formulation can occur.

In order to describe alternate materials useful in connection with thepresent invention, the synthesis of three amine-molybdate compounds willbe described hereinbelow, it being understood that each resultantcompound possesses appropriate physical and chemical properties in itsanhydrous form so as to be highly useful in connection with the variousaspects of the present invention.

The aliphatic amines employed are from the group consisting ofdicyclohexylamine, 2-ethylhexylamine, and cyclohexylamine, it beingunderstood that other aliphatic amines within this general category maybe found useful as well.

AMINE-MOLYBDATE "A"

Pursuant to this embodiment, dicyclohexylamine having a molecular weightof 181.36 and the empirical formula C₁₂ H₂₃ N is employed. The methodand procedure set forth in Example I hereinbelow is followed.

EXAMPLE I

A formulation is prepared with the following components:

    ______________________________________                                        Component          Percent by Weight                                          ______________________________________                                        Dicyclohexylamine  10%                                                        Phosphoric acid     4%                                                        Water              36%                                                        Aqueous solution of ammonium                                                                      50%.                                                      molybdate (20%)                                                               ______________________________________                                    

The 20% ammonium molybdate solution is prepared by adding puremolybdenum trioxide to a 5% aqueous solution of ammonium hydroxide. ThepH of the resulting solution is normally in the range of 7.5 to 8.5. Thedicyclohexylamine, phosphoric acid and water are mixed together to forma neutral to slightly alkaline solution, the pH being in the range of7.5 to 8.5. The 20% aqueous solution of ammonium molybdate is thenadded. The reaction that occurs is a simple displacement reaction inwhich a white powdery precipitate is formed upon addition of theammonium molybdate solution. Following the completion of the reaction,the mixture is cooled to approximately 60° F., after which theprecipitate is filtered, washed, and dried until the anhydrous form isobtained. The anhydrous finished product is a fine white powder havingthe following structural formula: ##STR2## wherein R₁ and R₂ arecyclohexyl radicals.

AMINE-MOLYBDATE "B"

Pursuant to this embodiment, 2-ethylhexylamine having a molecular weightof 129.2 and the empirical formula C₈ H₁₉ N is employed. The method andprocedure set forth in Example II hereinbelow is followed.

EXAMPLE II

A formulation is prepared with the following components:

    ______________________________________                                        Component          Percent by Weight                                          ______________________________________                                        2-ethylhexylamine  5%                                                         Phosphoric acid     2.5%                                                      Water              67.5%                                                      Aqueous solution of ammonium                                                                     25%.                                                       molybdate (20%)                                                               ______________________________________                                    

The 20% ammonium molybdate solution is prepared as set forth in ExampleI hereinabove. The 2-ethylhexylamine, phosphoric acid and water aremixed together to form a neutral to slightly alkaline solution, the pHbeing in the range of 7.5 to 8.5. The 20% aqueous solution of ammoniummolybdate is then added. The reaction that occurs is a simpledisplacement reaction in which a white powdery precipitate is formedupon addition of the ammonium molybdate solution. Following thecompletion of the reaction, the mixture is cooled to approximately 60°F., after which the precipitate is filtered, washed, and dried until theanhydrous form is obtained. The anhydrous finished product is a finewhite powder having the following structural formula: ##STR3## whereinR₁ is a 2-ethylhexyl radical and R₂ is hydrogen.

AMINE-MOLYBDATE "C"

Pursuant to this embodiment, cyclohexylamine is employed in thepreparation of cyclohexylamine-molybdate. Cyclohexylamine having amolecular weight of 99.17 and the empirical formula C₆ H₁₁ NH₂ isemployed. The method and procedure set forth in Example III hereinbelowis followed.

EXAMPLE III

A formulation is prepared with the following components:

    ______________________________________                                        Component         Percent by Weight                                           ______________________________________                                        Cyclohexylamine   20%                                                         Molybdenum trioxide (pure)                                                                      13%                                                         Water              67%.                                                       ______________________________________                                    

The water, molybdenum trioxide and cyclohexylamine are mixed togetherall at once. While mixing, the solution is heated to approximately 175°F. When the solution becomes clear, the mixture is cooled to 60°-70° F.,whereupon a grey-white precipitate forms. The precipitate is filtered,washed and dried until the anhydrous form is obtained. The anhydrousfinished product is a white crystalline powder with the followingstructural formula: ##STR4## wherein R₁ is a cyclohexyl radical andwherein R₂ is hydrogen.

The amine-molybdates as set forth above are, of course, employed inanhydrous form with the silica gel substrate. It has been found thatsuch molybdates, when employed in anhydrous form and deposited ontogranular silica gel will be readily incorporated into a foam or intoolefinic films such as polyethylene and polypropylene. Effectivemixtures of the amine-molybdate components are normally formulatedutilizing 70% by weight anhydrous amine-molybdate of the type shown inExamples I, II and III above, 25% sodium nitrite and 5% benzotriazole.As indicated in connection with such formulations discussed aboveutilizing anhydrous sodium molybdate, these formulations incorporateamine-molybdates A, B or C, are impregnated into foam at a concentrationof from about 1% to about 30% by weight or extruded into polyethylenefilm at a concentration of between 2% and 3% by weight.

In accordance with the examples, the aliphatic amine may be present inan amount ranging from between about 5% and 20%. In the interests ofcompleteness of the reaction involved, it has been found thatapproximately 10% by weight of the aliphatic amine produces a desirableend product. The reactions involved occur quite rapidly and have beenfound to go substantially to completion at room temperature.

While dicyclohexylamine, 2-ethylhexylamine, and cyclohexylamine havebeen indicated as the most desirable materials, it will, of course, beappreciated that certain conditions of end use along with certain otherconsiderations and parameters may dictate that somewhat smalleraliphatic chain lengths be employed. For example, use of the material insomewhat cooler environments may render it desirable to utilizematerials having a somewhat shorter chain length in order to achieve anappropriate degree of sublimation while exposed to ambience. Otherconsiderations may indicate utilization of such shorter chain lengths,as well.

As has been indicated hereinabove, and with attention being directed toFIG. 1 of the drawing, the vapor phase corrosion inhibitor-desiccantcomposite materials of the present invention are well adapted forextrusion with resinous film material typically employed in thepackaging industry. When employed as a member or layer of a laminate,and with continued attention being directed to the drawing, the filmgenerally designated 10 includes a first layer of plastic film 11 havinga metallic or metallizing layer 12 deposited thereon. Layer 13 oflaminate 10 is impregnated with the composite compositions of thepresent invention, with the solid particles being introduced into thefilm through co-extrusion techniques. For example, the amine-molybdateof Example I is prepared, and deposited as a fine white powder ontosilica gel to form a composite. The composite is introduced intoconventional polyethylene film. This impregnated film is, in turn,laminated to the metallized layer 12 of film 11 so as to form theultimate composite. Laminating techniques for such films are, of course,well known in the art. Metallized films of biaxially orientedpolyethylene terephthalate are readily bonded to and laminated withpolyethylene films of the type shown at 13. In like manner, theamine-benzoate composition earlier described is deposited onto silicagel to form a composite which is then introduced into film.

FIG. 2 is an cross-section of foam 15 which is impregnated with acorrosion inhibitor-desiccant formulation of the present invention. Thefoam 15 is an open-cell isocyanate-derived polymer as known in the art.Retained within the cells 16 are discreet particles 17 of theinhibitor-desiccant formulation. These particles 17 are distributedwithin the foam by immersing the foam in a liquid in which theinhibitor-desiccant formulation is dispersed. The immersed foam 15behaves much like a sponge in soaking up the loaded liquid to therebyachieve deposition of the inhibitor-desiccant formulation therewithin.Evaporation of the liquid results in impregnation of the formulation byparticles 17. The impregnated foam 15 can be supplied in a roll or coilform 20 as shown in FIG. 3, and can be provided with an adhesive backing22 for adhered retention at a site. A section 23 has been cut from theroll.

Providing the corrosion inhibitor-desiccant formulation of the presentinvention is a permeable capsule 30 as shown in FIG. 4 permits placementof the capsule in proximity to items to be protected. The body 32 of thecapsule 30 is constructed of plastic, while a cover 34 is made ofTyvek®, a polymer having permeability characteristics which permitemission of corrosion inhibitor for deposition on items to be protected.

Vapor phase corrosion inhibitor-desiccant composites of the presentinvention are also well adapted for retention and/or packaging withinmodestly porous envelopes or other enclosures. These envelopes may beformed of plastic film or plastic foam, or alternatively, may befabricated from cellulosic products such as paper or the like. Inaddition to being retained and/or packaged within envelopes orenclosures, the material may be placed upon or within an appropriatesubstrate formed of synthetic resin, foam or cellulosic materials.Typical examples of useful material include polyethylene, polypropylene,polymer foams, paper, and the like. When paper is employed, it ispreferred that the drying operation be undertaken so as to providereasonably anhydrous amine-molybdate materials.

It will be appreciated, therefore, that examples provided herein are forpurposes of illustration only and are not to be regarded as arestriction upon the scope of the claims, inasmuch as those skilled inthe art may depart from these specific examples without actuallydeparting from the spirit and scope of the present invention.

What is claimed is:
 1. A permeable capsule containing a vapor phasecorrosion inhibitor-desiccant formulation comprising a vapor phasecorrosion inhibitor component and a desiccant component, wherein thecorrosion inhibitor component comprises, by weight, from about 22% toabout 27% sodium nitrite, from about 4% to about 6% benzotriazole, andfrom about 65% to about 75% of an anhydrous molybdate selected from thegroup consisting of sodium molybdate, ammonium dimolybdate, aminemolybdates, and mixtures thereof, and wherein the desiccant componentcomprises a granular silica gel, with said corrosion inhibitor componentdeposited upon said granular silica gel.
 2. A permeable capsule asclaimed in claim 1 wherein the corrosion inhibitor component comprises,by weight, about 25% sodium nitrite, about 5% benzotriazole, and about70% of the anhydrous molybdate.
 3. A permeable capsule containing avapor phase corrosion inhibitor-desiccant formulation comprising a vaporphase corrosion inhibitor component and a desiccant component, whereinthe corrosion inhibitor component comprises, by weight, from about 50%to about 97% cyclohexylamine benzoate, from about 1% to about 20%ethylamine benzoate, from about 1% to about 20% dicyclohexylaminenitrate, and from about 1% to about 10% benzotriazole, and wherein thedesiccant component comprises a granular silica gel, with said corrosioninhibitor component deposited upon said granular silica gel.
 4. Apermeable capsule as claimed in claim 3 wherein the corrosion inhibitorcomponent comprises, by weight, about 68% cyclohexylamine benzoate,about 10% ethylamine benzoate, about 20% dicyclohexylamine nitrate, andabout 2% benzotriazole.